Sandra wrote:What's the the difference between positive and negative blood types?

A certain protein present in the blood of some people is referred to as Rhesus factor. If your blood does contain this protein, your blood is said to be Rh positive (Rh+). If your blood does not contain this protein, your blood is said to be Rh negative (Rh-).

It is particularly important for expectant mothers to know their blood's Rh factor. Occasionally, a baby will inherit an Rh positive blood type from its father while the mother has an Rh negative blood type. The baby's life could be in great danger if the mother's Rh negative blood attacks the baby's Rh positive blood. If this happens, an exchange transfusion may save the baby's life. The baby's blood can be exchanged for new blood that matches the mother's.

Red blood cells contain molecules which are labeled either A or B. If red blood cells have only "A" molecules on it, that blood is called type A. If the red blood cells have only "B" molecules on it, that blood is called type B. If the red blood cell had a mixture of both molecules, that blood is called type AB. If the red blood cell had neither A nor B molecules, that blood is called type O.

If two different blood types are mixed together, the blood cells may begin to clump together in the blood vessels, causing a potentially fatal situation. Therefore, it is important that blood types be matched before blood transfusions take place. In an emergency, type O blood can be given because it is most likely to be accepted by all blood types. However, there is still a risk involved.

People with type A blood can donate blood to a person with type A or type AB. A person with type B blood can donate blood to a person with type B or type AB. A person with type AB blood can donate blood to a person with type AB only. A person with type O blood can donate to anyone.

People with type A blood can receive blood from a person with type A or type O. People with type B blood can receive blood from a person with type B or type O. People with type AB blood can receive blood from anyone. A person with type O blood can receive blood from a person with type O.

Because of these patterns, a person with type O blood is said to be a universal donor. A person with type AB blood is said to be a universal receiver. In general, however, it is still best to mix blood of matching types and Rh factors.

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